84 MORPHOLOGY. 



saw them detach themselves and swim free in the cavity of the stomach. Here tliey 

 underwent further development, which he continued to observe until he saw them trans- 

 formed into true Cunina, differing, however, from the parent by the fact of their having 

 twelve tentacles and twelve stomach-pouches, instead of eight, the number characterising 

 the medusa which gave origin to them. Beyond this point Miiller lost sight of them, and we are 

 accordingly ignorant of their further changes and destination. 



But in no recorded case of the production of one medusa from another by budding is the 

 heteromorphism between the budding medusa and the buds produced by it so striking, and 

 nowhere has it been so fully traced as in the observations of Haeckel, described in his remarkable 

 memoir on the Gerjjonidm, in which he has shown that a sexually mature Geryonidan medusa 

 {Carmarina liastata, Haeckel), having its segments a multiple of six, produces upon the tongue-like 

 process which in this genus projects from the fundus of the stomach into its cavity a multitude 

 of buds which become developed, not into a six-rayed form resembling that of the Geryonidan 

 which gave rise to them, but into true Ciaiince, ^ginidan medusae having eight instead of six 

 elementary body-segments, and like all the yEginidan medusae belonging to a type which had 

 been previously regarded as possessing no relation whatever with the Geryonida. 



It is not alone in the fact that the buds belong to a very different medusa-type from the 

 budder that the phenomena described by Fritz Miiller and by Haeckel present features peculiar 

 and anomalous ; for the situation of the buds within the stomach cavity of the bud-producing 

 medusae is without parallel in any other group of Hydroida. In every case where medusa-buds 

 have been observed among other famihes of the Hydroida, the somatic cavity of the bud has 

 been in communication with some part of the somatic cavity of the hydroid which produces 

 it ; while here such a communication is impossible before the development of the mouth in the 

 bud shall enable the young ^ginidan to receive nutriment through this orifice from the stomach 

 cavity of the supporting medusa. 



Two other cases, however, both among the ^Eginidan type of the Geryonida — namely, that 

 of Cunina proli/era, described by Gegenbaur,^ and that of jEyineta gemmifvra, described by 

 Kcferstein and Ehlers' — have also been recorded, in which the young luedusse are formed as buds 

 within the cavity of the stomach, in both of these instances the buds having been developed from 

 the internal surface of the stomach walls. In all these cases the buds must have been formed in 

 a very different way from that which takes place in the ordinary cases of budding medusae — so 

 different, indeed, that were it not for the competency of the observers who have described 

 them as cases of true budding, we should be disposed to regard them as suggesting parasitism, 

 rather than gemmation. 



It is not, however, only in the Gcroiiykhe that we meet with cases of heteromorphic budding 

 from the medusa ; for the blastocheme, as we have already seen, is constructed on the plan of a 

 fully developed hydroid medusa ; while its sexual buds are simple sporosacs. 



' ' Generatioiiswcclisel,' p. 56. " 'Zeit. fur wisseu. Zool.,' 1853, p. 352. 



